Electrolytic cell



June U, 1945 w. GARDNER 2,401,821

ELECTROLYT IG CELL Filed Ot. 16. 1941 2 Sheets-Sheet 1 @mem/waar Y ZJ @f f 7 INVENTOR 4./ BY A I- MmLoMz-nmnd..

ATTORNEYS JJun'll, 1946.

Filed Oct. 16, 1941 w. c. GARDINER ELECTROLYTIC CELL 2 Sheets-Sheet 2 INVENTOR BY M41 bwa/M4 v 5MM ATToRNEyLS Patented June 11,1946

UNITED STATE ELEcTnoLYTIc CELL william c. Gardiner, Niagara Falls, N. Y., assignor to The Mathieson Alkali Works, Inc., New York, N. Y., a. corporation of Virginia Application October 16, 1941, Serial No. 415,276

My invention relates to improvements in electrolytic cells for the production of light metals from lfused salt baths heavier than the metal,

Claims. (Cl. 204-247) particularly for the production ofmagnesium from fused salt baths containing magnesium chloride. 'I he improvements' of my 'invention afford important economies with respect to cell construction, Vmaintenance and operation, and, as applied to fused chloride baths, facilitate the separation and recovery of chlorine liberated by the electrolysis in high concentration andv of high purity.

The improved electrolytic cell of my' invention is characterized essentially by an apertured, horizontal partition disposed below the normal bath level in the cell' chamber` and by the relationship of this partition to the other parts of the cell. The anodes, for the electrolysis, are suspended through the apertures in this partition, and the cathode elements, disposed around the anodes, and non-conducting sleeves, extending downwardly from the periphery of the apertures through which the anodes are suspended, are suspended from the partition. The otherparts of the cell of particular importance with respect to my invention comprise the elements establishing the circulatory path of the fused electrolyte and those establishing the compartment for charging the salt to be electrolyzed to the bath, the compartment for collecting the liberated metal and the compartment for collecting gas liberated by the electrolysis. My invention also includes a. particular varrangement of the cathode elements and a particular proportioning of the horizontal area of' the annular spaces between the sleeves suspended from the partition and the anodes suspended through the apertures in the partition and these sleeves.

An electrolytic cell embodying my invention is illustrated in the accompanying drawings. In these drawings, Figurel 1 is a vertical section, with certain details omitted, through the cell showing the charging compartment (at the right), the electrolysis compartment (at the lower left) and the gas collection compartment (upper left), on line I-I of Figure 2; Figure 2 is a. plan of the cell; Figure 3 is a. vertical section showing the metal collection compartment (at the upper right), the electrolysis compartment (at the lower lei't)v and the gas collection compartment (at the upper left) on line 3 3 of Figure 2; and Figure 4 is a vertical section through the charging compartment on line 4 4 of Figure 2.

Tne horizontal partition characteristic of my partition 6.

ported by the roof 'of a bell I2 forming a. gas colconstructed in the cell illustrated of steel plate protected and insulated on its upper surface-by appropriate refractories 6. The fact'that'this partition can be constructed in this manner contributes materially to the advantages of my invention. This horizontal partition 5 is disposed below the normal bath level, indicated at A in Figures 1 and 3, within a cell chamber 'l and two sides of this partition are separately spaced from the chamber walls to provideiafree surface in the charging compartment through which the electrolyzed salt can be introduced into the fused electrolyte and through which 'any liberated water, for example, can escape from the cell and to provide a separate free surface in the metal collection compartment from which the metal Vproduced by the cell can be removed, all without` exposure of the fused electrolyte in the electrolysis compartment and- Without requiring access to the gas collection compartment or passage of salt being charged to the cell through this compartment. The charging compartment and the metal collection compartment may be arranged along adjacentsides of the horizontal partition 5, as in the cell illustrated, or they may be arranged along opposite sides of this partition. Also the charging compartment may be arranged along one side of this partition and metal collection compartments along both of the adjacent sides. In the cell illustrated, the charging compartment 8 and the metal collection cempartment 9 are separated by the partition, or inverted dam, I which, as indicated in Figure 4, extends entirely across the upper part of this side of the cell chamber. A

The anodes II, carbon rods, are suspended through the indicated apertures in the horizontal These anodes, severally, are suplection chamber above -the partition 5. Each anode is carried by a water-cooled yoke I3, which may also serve as the anode terminal, by nuts on threaded pillars I4 secured to the roof of the bell I2, facilitating vertical adjustment of the anodes. Each anode passes through a. gas-tight seal on the roof of the bell made up of a pair of refracinvention is designated 5 in the drawings and is 65 tory bushings I5 and I6 and a packing of asbestos rope I1 and powdered magnesia 4I8 (see Figure 1). The roof of the bell is provided with a water-V cooled jacket space I9 (see. Figs. 1 and 3) to which water may-be supplied and from which it may be discharged via, inlet aperture I9a, and outlet aperture lsb, respectively (see Fig. 2). A non-conducting sleeve 20, of appropriate refrac- `tory material, passing through the apertures in respects. y

lments also should permit free circulation of the the partition 5 and extending downwardly from the periphery of these apertures and supported by the partition 5, is disposed around each of the anodes. 'I'hese sleeves 2B are with special advantage so proportioned with respect to the anodes Il and the cell capacity that the aggregate horizontal areas of the annular spaces be-l tween these sleeves andthe anode approximate A.0;014 square inch per ampere of cell capacity for above the horizontal partition 5. The cell illustrated can be enlarged by extending the cell along an axis normal to the section illustrated in Figure l and by a corresponding extension of the horizontal partition and the provision of additional pairs of anodes and groups of cathode elements similarly arranged, The anodes may conveniently number from two to ten, for example.

In the illustrated cell, the cathode elements consist essentially of steel rods 2 I, suspended from the partition 5 and extending well below the lower rims of the sleeves 2li. As illustrated, the rods 2l are reinforced at their upper and lower ends, respectively, by hoorn 22 and 23. The rods 2| are disposed as elements of inverted frustoconical surfaces, that is with the larger base of the frustoconical section at the top, at all points more remote from the adjacent anode than the projection at the same level of the inner surface of the corresponding sleeve 20. The cathode elements may be otherwise disposed, for example as a cage or net, but are with advantage disposed as elements of inverted frustoconical surfaces at all points more remote from the adjacent anode than the projection at the same level of the inner surface of the corresponding sleeve irrespective of their arrangement or configuration in other The arrangement of the anode' elefused electrolyte into and through the space between the anode and -the cathode elements. The cathode elements are with advantage electrically connected to a steel plate forming the partition 5, by welding for example, and thus connected to the cell chamber, of cast steel or steel plate for example, to which the cathode terminal is then ailixed.

An inverted dam 24, thatfis adam establishing flow beneath itself, extends downwardly from that side of the partition 5 spaced from the wall of the cell chamber 1 to form the charging compartment 8, preferably to a level somewhat below the through the 'charging compartment to the lower part of the cell chamber and beneath the dam 24 backv to the electrolysis chamber. The salt to be electrolyzed issupplied to the fused electrolyte circulating within the cell chamber to maintain the'concentration of this component as it is consumed by the electrolysis by introduction into the charging compartment 8, for example, throughv removable covers'2t` or through a connection 21. In the feeding compartment, the salt thus supplied is fused and incorporated into the circulating fused electrolyte 'moving from the charging compartment to the electrolysis compartment beneath the inverted dam 24. In the production of magnesium, magnesium chloride may thus be' supplied to a fused electrolyte comprising, in addition to magnesium chloride, one or more of a variety vof salts such as sodium chloride, sodium fluoride, potassium chloride, calcium chloride and calcium uoride. The magnesium chloride may thus be supplied as the anhydrous salt or it may be supplied in hydrated condition, for example as the dihydrate, in which event dehydration is also effected in the charging compartment, liberated water being exhausted through connections 2B t0 appropriate evacuating equipment. The arrangement of the dams I0 and 24' just described, and illustrated in the drawings, also makes the charging compartment an advantageous means of access for dredging the cell to eliminate solids settling from the fused electrolyte within the cell chamber, -solids such as magnesium oxide in the electrolysis of magnesium chloride. To facilitate such dredging of the cell, the cell chamber l is with advantage arranged with a.- bottom sloping toward the side beneath the charging compartment, as illustrated in Figure 1, to form a collection trough 2Q to which direct access can be had through the charging compartment. This configuration of the bottom of the cell chamber, particularly with respect to the inverted dam 24, also promotes settling of any suspended impurities in the fused electrolyte at this point. If hydrous magnesium chloride is introduced into the charging compartment, for example, any magnesium oxide produced by hydrolysis during dehydration of such magnesium chloride in the f charging compartment tends to settle in the trolyte during operation is with advantage limlower ends of the anodes and cathodes in the elec` i trolysis compartment. This dam may be of steel plate, and .may be connected electrically to a steel plateformlng the partition 5. The inverted dam I0 extends downwardly from above the bath level to belowthe bath level above this same side of trough '29 as the fused electrolyte circulates beneath the dam 24 before entering the electrolysis chamber, With this arrangement, any external ring of the cell chamber to assist in maintaining temperatures necessary for-fusion of the elecited to that part of the cell chamber to the left of the point approximately located at C in Figure 1.

An auxiliary dam 30 (see Figure 1) extending upwardly from the partition 5`below .the bath level and spaced from andparalleling the side of this partition beneath the dam I0 and above the dam 24 is with advantage provided to assist in maintaining the uniformity of flow of the fused electrolyte, particularly, through the charging compartment, and also assists in effecting complete separation of gas liberated by the electrolysis A in the space above the partition 5. Gas separated in the space above partition 5 may be withdrawn from th'e gas collection compartment 31 through vent 4i The metal liberated on the cathode elements in the electrolysis compartment rises through the fused electrolyte to the lower side of the partition 5 beneath which it is trapped by that part of the sleeves 20 extending downwardly from the periphvery of the apertures through the partition 5. The

disposition of the cathode elements previously described, particularly in the electrolysis of fused chlorides with the proportioning previously described, effe'ctively secures substantially complete recovery of the liberated, fused metal as a layer vrbeneath vthe partition 5 of depth less than the extending upwardly Vfrom the partition 5 (see Figure 3) where it floats on the fused electrolyte at a somewhat higher level, indicated at B in Figure 3, than the lbath level because ofthe lower density of the liberated metal. The partition 3|, in conjunction withA the partition 5, the end of the partition l extending beyond the partition 5 and the walls of the cell chamber connecting these two partitions, establish the metal collection compartment 3. Removable covers 34, 35 and 36, are provided to facilitate removal of the liberated metal collected in the compartment 9. The sides of the removable covers 34, 35 and 36 adjacent the partition 3| are supported by the support 32 (see'Fig.-3). The opposite -edges of thesel covers maybe supported by an inward ex- 6 mately 8 inches in diameter. 'I'he cell of the drawings is illustrated approximately to scale, the anodes of this cell being approximately 8 inches in diameter.

I claim: l. `In an electrolytic cell for the production of light metals from fused salt baths heavier than the metal, the improvement which comprises a cell chamber, a horizontal partition disposed below the normal bath level therein and'separately v spaced from the chamber walls on two sides said partition being shaped to provide apertures therein, anodes suspended through said apertures,

non-conducting sleeves extending downwardly from the periphery o f said apertures the upper end of said non-conducting sleeves being disposed below the normal bath level, a partition extending upwardly to the top of the cell chamber from tension 43 of the wall of the cell chamber 1, as

shown in Fig. 3.

The gas collection compartment 31 above the horizontal partition 5 is formed by a gas collecting bell with its lower edge disposed below the bath level but spaced above that side of the partition over which the electrolyte iiows to the charging compartment.

In the cell illustrated,

this bell l2 is made up of a water-cooled roof and walls fabricated of steel plate and lined with appropriate refractories 38. A gas ti'ght gas collection chamber is thus assured. The walls of the bell extend downwardly to a level below the bath level and within the walls of the cell chamber and, with advantage, into a groove arranged to conform to the lower edge of the bell to permit insulation of the metal elements of the bell struc ture from the anode in order to prevent liberation of traces of metal -by electrolysis above the partition 5. In the cell illustrated, this groove appears at 39 -(see Figures 1 and 3). In practice, that part of this groove adjacent the metal of the bell structure is packed with a refractory cement and the innerpart of the groove isleft open. In the electrolysis of magnesium chloride, for example, magnesium oxide tends toaccumulate in the remaining portion of the groove to space between the walls of the bell and the surrounding walls of the cell chamber 'Iv and the partitions I0 and 3| is advantageously packed with a pulverulent reducing material such as pulverized coke as indicated at 40 '(see Figures 1 and 3). The metal elements of the cell structure, above the level of the horizontal partition 5, should be appropriately protectedy with refractory material against the fused electrolyte and the atmosphere above it. Acid-resistant brick and porcelain tile, capable of withstanding the temperatures involved, are appropriate refractories.

Electrolytic cells embodying my invention can be operated for the vproductionA of magnesium from magnesium chloride fusions, for example, with current capacities of about 3000 to 3500 amperes per anode using carbon anodes approxiverted dam last mentioned and the anodes andform a frangible and non-conducting seal. The

one of said spaced sides of the horizontal partition, an inverted dam vextending downwardly from the other of saidl spaced sides, an inverted dam extending downwardly from the top of the cell chamber to below the bath level above the spaced side last mentioned and forming a gas seal with the bath, cathode elements suspended from said horizontal partition and disposed around said anodes, and a trough in the bottom of the chamber to one side of the anodes and said inverted dam that extends downwardly from the horizontal partition with the sides of the chamber sloping downwardly to the trough.

2. In an electrolytic cell for the production of light metals from fused s alt baths heavier than the'metal, the improvement which comprises a cell chamber, a horizontal partition disposed below the normal bath level therein and separately spaced from the chamber walls on two sides, said partition being shaped to provide apertures therein, anodes suspended through said apertures, non-conducting sleeves extending downwardly from the periphery of said apertures the upper ends of said non-'conducting sleeves being disposed below the normal bath level, /a partition extending upwardly to the top of said cell chamber from vone of said spaced sides of said horizontal partition, an inverted dam extending downwardly from the other of said spaced sides, a second inverted dam extending downwardly from the top of the cell chamber to below the bath level 'above the spaced side last vmentioned and forming a gas seal with the bath, a

dam extending upwardly from said horizontal,`

partition and spaced from and paralleling the spaced side last mentioned, said upwardly extending dam being positioned between -the interminating at its upper end below the bath level, and cathode elements suspended from said horizontal partition and disposed around said anodes.

3. In an electrolytic cell for the production of light metals from fused salt baths heavier than the metal, the improvement which comprises a cell chamber, a horizontal partition disposed below the normal bath level therein and separately spaced from the chamber walls on two sides, said partition being shaped to provide aper- I, tures therein, anodes suspended through said apertures, non-conducting sleeves extending downwardly from the periphery of said apertures the upper ends of said non-conducting sleeves being` disposed below the normal bath level, cathode elements suspended fromsaid horizontal partition and disposed around said anodes and extending below said sleeves, Asaid cathode elements consisting essentially oi'k spaced downwardly extending rods disposed as elements of inverted frustoconical surfaces at' all points more remote from the adjacent anode than the projection at the same level of the inner surfaces of the corresponding sleeve, said rods being held in such a position by rings disposed around the anodes, a partition extending upwardly to the top of said 'cell chamber from one of said spaced sides .of` said horizontal partition, an inverted dam extending entirely across the cell chamber and downwardly from the other of said spaced sides a of said horizontal partition, a second inverteddam extending entirely across the cell chamber and downwardly from the top of the `cell chamber to the upper edge of the inverted dam ilrst mentioned and forming a gas seal with the bath,

Asaid second-mentioned inverted dam being shaped to provide a passageway positioned above said horizontal partition and below the normal bath level, and a dam extending upwardly from said horizontal partition and spaced from and paralleling the spaced side last mentioned, said upwardly extending dam being positioned between the inverted dam last mentioned and the anodes and terminating at its upper end below the bath level. v

4. In an electrolytic cell for the'productlon of light metals from fused salt baths heavier than Y the metal; the improvement which comprises a cell chamber, a horizontal partition disposed below the vnormal bath level therein and separately spaced lfrom the chamber walls on two sides, said partition being shapedto provide apertures therein, anodes suspended through said apertures, non-conducting sleeves extending downwardly from the periphery of said apertures the upper ends of said non-conducting sleeves being disposed below the normal bath level, cathode elements suspended from said horizontal partition and disposed around said anodes and 8 wardly` from the top of the cell chamber to lthe upper edge of the invertedl dam nrst mentioned and forming a gas seal with the bath, said secondmentioned inverted dem being'shaped to provide a passageway positioned above said horizontal partition and below the normal bath level, anda dam extending upwardly from said horizontal partition and spaced-from and paralleling the inverted dam last mentioned. said upwardly extending dam being positioned between the in- Verted dam last mentioned and the anodes and terminating at its upper, endbelow the bath level. 5. In an electrolytic cell for the production of 'light metals from fused salt baths heavier thanA ing upwardly to the top of' said cell chamber l from one of said spaced sides of said horizontal extending belowsaid sleeves, the aggregate horizontal areas of the annular spaces between said sleeves and said anodes approximating 0.014 square inch per ampere of cell capacity, a partition extending upwardly to the top of said cell chamber from one of said spaced sides of said horizontal partition, an inverted dam extending entirely across the cell chamber and downwardly from the other of said spaced sides of said horizontal partition, a second inverted dam extending entirely across the cell chamber and-downpartition, an inverted dam extending" entirely across the cell chamber and ydownwardly from the'other of said spaced sides of said horizontal partition, a second inverted dam extending entirely across the cell chamber and downwardly from the top of the cell chamber to the upper .edge of the inverted dam iirst mentioned and forming a gas seal with the bath, said secondmentioned inverted dam being shaped to provide a passageway positioned above said horizontal partition and below the normal bath level, a dam extending upwardly from said horizontal partition and spaced from and paralleling the inverted dam last mentioned, said upwardly extending dam being positioned between the inverted dam last mentioned and the anodes and terminating at its upper end below the bath level, and a gas collecting bell disposed above said horizontal partition with its lower edge extending below the normal bath level.

WILLIAM C. GARDINER. 

